Leptin deficiency and beta-cell dysfunction underlie type 2 diabetes in compound Akt knockout mice

Area of Science:

• Molecular Biology
• Metabolic Diseases
• Endocrinology

Background:

• The individual roles of Akt isoforms (Akt1, Akt2, Akt3) in glucose homeostasis and diabetes remain incompletely understood.
• Previous studies suggested Akt2 is the primary isoform involved in diabetes, with others playing distinct roles.

Purpose of the Study:

• To investigate the compensatory and complementary roles of Akt isoforms in glucose homeostasis and the development of type 2 diabetes.
• To explore the underlying mechanisms of diabetes in Akt isoform-deficient mice and identify potential therapeutic targets.

Main Methods:

• Phenotypic analysis of mice with targeted deletions or deficiencies in individual Akt isoforms (Akt1, Akt2, Akt3) and combinations thereof.
• Investigation of insulin resistance, beta-cell function, and leptin levels in genetically modified mouse models.
• Assessment of the impact of Pten (a negative regulator of Akt) haplodeficiency on diabetes development.

Main Results:

• Akt isoforms exhibit compensatory and complementary functions in maintaining glucose homeostasis.
• Akt2 deficiency alone caused insulin resistance, which was ameliorated by Pten haplodeficiency, indicating Akt1/Akt3 compensation.
• Combined Akt1 and Akt2 deficiency (Akt1(+/-) Akt2(-/-)) led to overt type 2 diabetes, characterized by hyperglycemia, beta-cell dysfunction, and significantly decreased leptin levels.
• Restoring leptin levels normalized blood glucose and insulin levels in Akt-deficient diabetic mice.
• Akt3 did not appear to play a significant role in diabetes development.

Conclusions:

• Akt isoforms have complex, interconnected roles in glucose metabolism and diabetes.
• Leptin deficiency is a critical factor driving diabetes in Akt1(+/-) Akt2(-/-) mice.
• Leptin therapy presents a potential strategy to reverse diabetes induced by Akt inhibition, such as in cancer therapy.